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I think i have to do it manually. this is what it says:Take as an example the first and second spot

elevations in Row 1 (elevations 88.9 and 93.. The
90-foot contour line is somewhere between these
two spot elevations. The difference between the
values of these elevations (93.8 88.9) is 4.9 units.
Try visualizing the difference in elevation between
the two points as divided into intervals of

1/10 units.
There would thus be 49 of these 1/10 units between

the two points. The 90-foot contour line comes

between the two points at one of these

1/10 units.
To be precise, the distance from the first spot elevation
to the 90-foot contour line is 1.1 units (90
88.9). Thus, the contour line is exactly 11 of the

1/10

units away from the first spot elevation. In
other words, you divided the line between spot elevations
into 49 equal lengths, based on the change
in elevation. The contour line will come between
the spot elevations at 11 of these lengths counted
from the first spot elevation. In this way, you’ve
estimated, with a certain degree of precision, where
the 90-foot contour will intersect the line between

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I went through the course in 08-09. I no longer have the instructions. But I remember that each conture line position had to be calulated on the X and Y. Recheck the instructions, I think that it gives this one example. Then you have to do the rest on your own.

this part is the one talking obut the x and y.
The area is located in a state that bases all surveys on
the intersection of a meridian and a baseline for that
state. Therefore, the origin (or point 0,0) for all surveys is
at that intersection, and any X and Y coordinates tell the
distance in feet from the intersection. If, for example, a
benchmark is at point 11675,39532, the benchmark is
2.21 miles east of the intersection and 7.49 miles north

What is/are 'contour line footages'? Is that contour intervals in feet (instead of the S.I. Metres)?

Can you post up/send me the details of the whole assignment to look at so I have some idea as to it exactly.

In the real world you are not going to interpolate contours anymore like that. Any decent company will hire a surveyor to survey the land and provide a dtm and contours (which are obtained via interpolation and more sophisticated computer algorithms in software packages). You just need to be able to identify what is happening and if the software is correct (as it can be wrong) and adjust it as necessary.